Rate Constant Determination for Saponification in Batch & CSTR by HC11120920136

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									Rate Constant Determination for
Saponification in Batch & CSTR

        February 17, 2005

   Presentation by Trevor Binney
        Group Members

         Jay Berndt      Me    Eric Houchin
Operations Manager   Team Leader   Safety Coordinator
           Presentation Plan
•   Familiarize audience with saponification
•   Discuss the project objectives
•   Overview of process and equipment used
•   Batch and CSTR kinetic data results
•   Difficulties encountered during lab work
•   Give recommendations for future work
•   Answer any questions the audience have
•   CSTR-   Continuous Stirred Tank Reactor
•   EtAc-   Ethyl Acetate
•   NaAc-   Sodium Acetate
•   EtOH-   Ethyl Alcohol (Ethanol)
•   PPE-    Personal Protective Equipment
•   Soln-   Solution
•   Xa-     Extent of Reaction of NaOH
•   Conc-   Concentration in mol/L
•   Ca-     mol/L NaOH
         What is Saponification,
         and what is it used for?
• http://www.dictionary.com/ defines saponification
  as: A reaction in which an ester is heated with
  an alkali, such as sodium hydroxide, producing a
  free alcohol and an acid salt, especially alkaline
  hydrolysis of a fat or oil to make soap.
•    EtAc   +    NaOH      NaAc       +     EtOH
• Saponification is primarily used for the
  production of soaps.
           Project Objectives
Our team was asked to meet several goals
   while running saponification experiments

  1. Develop conductivity calibration curves for the
     reactants used in the process. (NaOH & EtAc)
  2. Verify feed concentration through
     standardization using titration
  3. Determine the true rate constant for reaction in
     a batch reactor
  4. Obtain reaction rate data for the CSTR as a
     function of the solution residence time
       Safety Considerations
• NaOH- Corrosive
• EtOH & EtAc- Flammable
• EtAc will corrode various plastics
• Standard PPE worn, as well as face shield and
  rubber gloves for handling dangerous chemicals.
• Clean up spills and broken glass immediately
• Be aware of where other people in the lab are
• Open windows for ventilation and work under
  the fume hood when mixing solutions
•   Conductivities EtAc & EtOH negligible
•   Solution inside the CSTR is well mixed
•   Solution inside batch reactor well mixed
•   Ethyl acetate bottle wasn’t contaminated
•   Liquid pulled from the “1 M” EtAc is 1 M
•   The CTSR flow meters were accurate
•   Conductivity linearly proportional to Conc
Conductivity Probe Calibration
Conductivity Probe Calibration
                              NaOH Conductivity vs Concentration

                                         y = 214.03x
Conductivity (mho)


                     30                                              Literature Data

                     20                                              Calibration

                     10                                              Linear (Literature
                          0     0.05    0.1            0.15    0.2         0.25           0.3
                                               Molarity NaOH
    Xa & Conc Solved w/ Conductivity
•   NaOH conductivity: 214*(conc NaOH) mS/m
•   NaAc conductivity: 78*(conc NaAc) mS/m
•   EtAc & EtOH conductivity: negligible
•   Overall conductivity: Ca0*(214-136*Xa)
•   Where Xa = (Ca0 – Ca) / Ca0
Continuous Stirred Tank Reactor
             CSTR procedure
1.   Enter setpoint temperatures using set point 2
2.   Drain reactant tanks as much as possible
3.   Prepare three liters of reactant solutions
4.   Fill tanks equally and heat to set temp
5.   Make sure the bottom reactor drain is closed
6.   Turn on the CSTR stirring device
7.   Open the flow valves to equal levels
8.   Wait until SS reached and record conductivity
     using a calibrated conductivity probe
Batch Reactor and Heating Bath
            Batch Procedure
1. Preheat bath to desired reaction temp
2. Prepare the NaOH and ethyl acetate solutions
3. Fill two erlenmeyer flasks, one with NaOH and
   the other with EtAc
4. Allow reactants to heat to desired temp
5. Pour one flask into the other submerged flask
6. Using the conductivity probe, record
   conductivities of the solution every 15 seconds
7. Record data until the conductivity stabilizes
 Equations Used for Data Analysis
• Arrhenius’ law:         k = k0e-E/RT
     • ln(k2/k1)=E/R*(1/T1 – 1/T2)
• Ca0*(214-136*Xa)
• Xa = (Ca0 – Ca)/Ca0
• Ca = (Cond/Ca0 – 214)*Ca0/136 + Ca0
Results and Conclusions
Results and Conclusions
      Results and Conclusions
• (k) Determined rate constant for saponification
• Experimental k = 0.178 L/mol*sec @ 30 °C
• Experimental k = 0.192 L/mol*sec @ 45 °C

• As listed in in the Bulletin of the Chemical
  Society of Japan k = 0.112 L/mol*sec
      • According to this source, the rate constant we
        determined was about 59% too large
      • A possible reason for this is that the EtAc solution
        concentration was higher than predicted
CSTR Results and Conclusions
Data recorded was very inconsistent
  – For equal feed concentrations, we had runs
    that yielded conductivities of 6-7 mS and also
    3 mS/m, with no results falling in between
    • Reagent bottle contamination?
    • Inability to completely drain feed tanks
    • Difficulty in maintaining stirring speed
  – CSTR operations were abandoned for the
    final lab period to focus on Batch data
Temperature Dependence Results
Multiple trials were run at both 30 & 45 °C
• Arrhenius’ law:     k = k0e-E/RT
• Rewritten:     ln(k2/k1)=E/R*(1/T1 – 1/T2)
• R = 8.314 J/mol*K
• E = Activation energy of this reaction
     We were unable to find the value for E in literature
k30 = 0.178 L/mol*sec < k45 =0.192 L/mol*sec
Experimental E = 4040 J/mol
          Overall Conclusions
• Saponification rxn is a 2nd order reversible reaction
  – (1/Ca vs time linear at low time)
• -Ra = k*Ca*Cb
• Considerable error comparing experimental
  rate constant to that in literature
• Batch data fairly reproducible and precise
• CSTR data and operation inconsistent
Difficulties Encountered During Lab
• Creation and mixing of ethyl acetate solns
  – Attempted creation of “1 M” stock solution
     • Attempted to dissolve 9.6 g EtAc/100 mL
     • Max Solubility of EtAc in water is 8 g/100 mL
  – Possible reagent bottle contamination
     • Evident through formation of unknown precipitate
• CSTR temperature reading inconsistency
• Inability to completely drain CSTR tanks
  Recommendations For Future Work
• Do research before entering the lab
• Become familiar with analytical equipment
• Begin trials with CSTR as early as
• Split up tasks for each person to do during
  lab prior to running the labs
• Make an in depth Design of Experiment
  before entering the lab
• Levenspiel, Octave. Chemical Reaction
  Engineering, Third Edition. USA: John Wiley &
  Sons, 1999.
• Levenspiel, Octave. The Chemical Reactor
  Omnibook. Corvallis, OR: OSU Book Stores, 2002.
• Pecaj, Arta. Personal Interview. February 16, 2005.
• Tsujikawa, H. and Inoue, H. 1965. The Rate of the
  Alkaline Hydrolysis of Ethyl Acetate. Bulletin of the
  Chemical Society of Japan. 39: 1837-1839
• http://www.woodlandsinstruments.com/conductivity_
Questions ??

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